Here, in 80 Page Giant #10 (May, 1965), is a collection of some of Superboy's greatest foes....the worst of the worst menaces the young Boy of Steel had to face as he grew into Superman-hood, all under a cover by Curt Swan and George Klein.
Adventure Comics #205
This story has Superboy meeting up with Kral, a young lad from Titan, Saturn's moon, who lands at the Kent homestead. The lad, like Superboy, is an orphan, but Kral is also an advance scout for an invasion fleet from Titan. Kral works with Superboy, learning of Earth's defenses and Superboy's weaknesses, and takes the Boy of Steel to Titan, planning to expose him to Kryptonite. While on Titan, Superboy shows the moon's leaders his powers, claiming all Earthmen have them. Kral, who was touched by his time on Earth, doesn't expose Superboy's lie to prevent a war neither want, and the two super-powered lads part as friends.
Adventure Comics #250
This time around, the invader is from the future, a criminal called Lorac-7, who has come to the past to steal cobalt. Superboy is ready, protecting the cobalt of Smallville, but can't help but suspect those around him, including his principal, Professor Lang, and even the mayor....until he realizes Lorac-7 is disguised as Lana Lang, whom he catches, and sends back to the future, but without her getting any cobalt for her evil plans.
Oddly, this villain had no connection to the Legion of Super-Heroes, but, to be fair, they had only appeared once before this, three issues prior.
Superboy and Krypto are both having dreams of a menace, that of the Kryptonite Kid and his dog, but this nightmare proves to be real, as the Kryptonite Kid and his dog show up to chase the Boy and Dog of Steel out of Smallville. Clark and his pet won't go, but a villain with the power to turn things into Kryptonite almost proves too much of Kal-El, at least until Mxyzptlk shows up, banishing the villain and his mutt, as Mxyzptlk wants the honor of finishing off Superboy one day (which he can't do if this new villain does).
Along with Kryptonite Kid's dog, Krypto faced other canine menaces, which they detail in a one page feature here, including Luthor's dog, Destructo.
Adventure Comics #271
It's an origin as old as time. Boy saves superhero from Kryptonite meteor, superhero creates boy (who is a fan) a super scientific lab, boy makes big breakthrough, but is careless and starts a fire, superhero breaks into lab to stop the blaze, causing the boy's hair to fall out, creating his greatest foe!
Luthor, of course, is the biggest threat to Superboy, and later, to Superman, and even rated his own Giant (though, it was battles with Superman), and this tale was also reprinted larger than life in a Limited Collectors' Edition (as well as other places).
Adventure Comics #264
Superboy faces off against Space-Boy, the alien Zall-Dix, who has come to Earth, looking to exchange minds, with this new alien taking the place of Superboy. Superboy obviously objects to this, so Space-Boy causes Superboy's powers to malfunction, making the Boy of Steel a menace to his town. Superboy finally does agree to the mind-swap, but, Clark's dad, Jonathan Kent, interferes, which impresses Space-Boy, who heads out into space towards home.
Adventure Comics #255
Kozz, an alien from Mars, uses Red Kryptonite to split the Boy of Steel into two...Superboy and Clark Kent! Superboy has powers (and morals) while Clark Kent has neither. This causes problems, with Clark leaving the Kent household (with Kryptonite). Superboy takes on a new identity, as Flying Spirit, a native American. Clark uses the Kryptonite and even Lana Lang to search for Superboy, and eventually the two battle, using Superboy robots. Clark wins by cheating, but damages his robot control device, which explodes, killing him, allowing Superboy to go back to being Clark Kent.
This wasn't the first time Clark Kent would face off against his heroic alter ego, and wouldn't be the last, as Superman and Clark Kent had many fights over the years!
100 Page DC Super Spectaculars, and many oversized issues of his own title as well, committed to his adventures, as well as those of other young heroes.